A finishing process employing solid-gas pellets



I Jan. 21, 1969 w, BALZ 3,422,580

FINISHING PROCESS EMPLOYINGQOLID-GAS PELLETS Filed Oct. 20, 1965 FINISH/N6 FINISH/N6 MACH/IVE MACH/IVE 4 V/BRA TM/G d l/IBRA rm/s SCREEN .SCREL'N uau/o HEAT BATH CH/IMBER I/IBRA TING SCREEN lo TVP/CAL CHIP 5&3?

Q... Z1 .5 TURN OVER DEVICE 12 a i V/BRAT/NG SCREEN -15 00650 7 CHIPS United States Patent 3,422,580 A FINISHING PROCESS EMPLOYING SOLID-GAS PELLETS Gunther W. Balz, Kalamazoo, Mich., assignor to Roto- Finish Company, Kalamazoo, Mich., a corporation of Michigan Filed Oct. 20, 1965, Ser. No. 498,972

US. Cl. 51314 Int. Cl. B24b 1/00; C11d 3/14; C08 17/12 The present invention relates to the finishing art and is more particularly concerned with a novel finishing composition and a method for removing finishing composition pellets and portions thereof which are entrapped in the cavities of finished parts.

Finishing of parts, as for example metal parts prepared by machining or casting, is generally accomplished by tumbling or vibrating the parts in a chamber together with a finishing composition to cause relative motion between the parts and the finishing composition. Such composition generally comprises either a mixture of relatively large pellets utilized as a bulking agent, together with a more finely divided abrasive material. Alternatively, the composition may comprise relatively large size pellets in which the more finely divided abrasive material has been dispersed, either uniformly or alternatively concentrated at the surface, center, or some other area thereof. Such pellets, or chips as they are commonly termed, may be prepared in any of many different forms such as triangles, rings, stars, bars, cylinders, tubes, and various other suitable forms.

Occasionally cast, molded, or madhined parts are finished which have cavities, recesses or apertures provided therein as, for example, automotive carburetors. Some difficulty has been encountered in the finishing of such parts in that the pellets or chips often become entrapped or wedged in such cavities and recesses during the finishing process, and are not removed by ordinary separation methods, but must subsequently be removed individually by manual means. This additional step involving hand labor adds considerably to the cost of the finishin g process.

It is accordingly an object of the present invention to provide an improved method for separating finishing material comprising relatively large pellets or chips from the recesses and cavities of parts in which they become lodged and entrapped. It is another object of the invention to provide such a method which may be relatively simply and inexpensively carried out as a part of an automatic finishing process, and without the necessity for special manual handling. It is a further object to provide novel finishing compositions, especially those comprised of ice, which are uniquely adapted for use in and with the method of the present invention. Additional objects and advantages will be apparent to one skilled in the art, and still other advantages will become apparent hereinafter.

The invention in its preferred embodiment is illustrated by the accompanying drawing in which:

FIG. 1 is a flow diagram of one embodiment of a process according to the invention.

FIG. 2 is a flow diagram of a process constituting a modified embodiment of the invention.

FIG. 3 is a side elevation of a typical pellet or chip; and

FIG. 4 is a fragmentary cross-section of a part showing a plurality of chips entrapped in certain cavities thereof.

According to the invention, a finishing composition is provided comprising chips or pellets, usually of relatively large size compared to the size of the associated abrasive particles, and an abrasive material. The abrasive material may be provided as separate finely divided or particulate material, in which case the pellets or chips are utilized in 6 Claims the capacity of a bulking agent. Alternatively, the abrasive particles may be dispersed within the chips, either uniformly or concentrated at the surface or center or at another particular portion thereof. A further alternative involves the use of abrasive material either free or dispersed in a usual pel et or chip matrix together with the unique bulking material of the invention. A still further alternative involves use of abrasive material partly in a normal or usual pellet or chip matrix and partly in a matrix according to the invention. Other alternatives will be obvious. The material from which the chips are produced is so chosen that it has certain physical properties which have different values than the comparable properties of the parts to be finished. In the embodiment of the present invention, the material is chosen to melt or sublime under such temperature conditions which leave the parts to be finished unaffected. Consequently, as an additional step in the finishing process, in order to remove chips which may have become entrapped within cavities of the part to be finished, the parts containing entrapped pellets are sub jected to temperature conditions of sufficient nature and magnitude to cause melting or subliming of the chip material to take place, but which leaves the parts unaffected. As a consequence, the pellets or chips become disengaged from the cavities of the parts and are readily separated therefrom.

Reference is now made to the accompanying drawing for a better understanding of the invention, wherein all the parts are numbered and wherein the same numbers are used to refer to corresponding parts throughout.

FIG. 1 is a flow diagram illustrating one embodiment of the method of the present invention. As shown, the parts and fiinishing composition are first subjected to a finishing process which may involve any one of many such methods and apparatus as commonly used, as for example a deburring process in a suitable finishing apparatus 1. After the parts have been properly finished, the mixture comprising the parts and finishing composition is removed from the finishing machine and the parts separated from the unentrapped finishing composition by means of an apparatus such as a vibrating screen 2. The separated parts, which may contain entrapped finishing pellets, are then transferred to an inert liquid bath, such as a water bath 3. The liquid bath 3 is maintained at a temperature sufficiently high to soften, fuse, or sublime the material of which the chips are fabricated. This temperature is sub stantially lower than the temperature required for causing a similar change in the parts. Such change of state of the pellets or chips permits them to be dislodged from the openings or cavities of the parts and to fall to the bottom of the bath, where they may be removed or recovered by suitable means (if in their changed state they are so removeable and/ or recoverable and worth the recovery effort). Where the parts contain cavities at their upper surfaces which continue to retain the dislodged chips, they may be subjected to a tumbling operation to permit the contained chips to be removed by means of gravity. Such chips may subsequently be removed by any suitable means such as a vibrating screen.

FIG. 2 illustrates another embodiment for use with pellets for which the temperature required to cause melting or sublimation is higher than that which can be conveniently obtained by means of a liquid bath. In this process, after proper finishing in a suitable finishing machine 4, the parts are separated from the unentrapped finishing composition by any suitable means such as a vibrating screen 5. The separated parts, containing entrapped chips, are then conveyed to a heat chamber 6 maintained at a temperature sufficiently high to cause the material from which the chips are made to melt or sublime. The mixture comprising the finishing composition and parts is then conveyed over a vibrating screen 7 for removing the dislodged chips. The separated parts, where necessary, may be transferred to a turnover device 8 for separating chips still remaining in upper cavities, and the separated chips removed over a second vibrating screen 9.

One commonly used type of chip or pellet 1G is illustrated in FIG. 3, and shown imbedded in various cavities of a part in FIG. 4. The part shown in fragmentary crosssectional view comprises a carburetor 11 having openings or cavities 12, 13, and 14, in which are wedged chips 15, 16, and 17. Upon entrance of the part into the heating chamber, chips such as 16 and 17 are readily dislodged. However, in order to dislodge chips such as contained in upwardly directed cavities, it is usually necessary to subject the part of a turnover device 8 as shown in FIG. 2.

The composition of the finishing material may be one of several types. In one embodiment the chips themselves do not contain any abrasive material, but are utilized primarily as a bulking agent, applying a force pressing the abrasive material against the surface of the parts. The abrasive comprises a separate component, generally in finely particulate form. Alternatively, the abrasive material may be dispersed or imbedded within the chips, either uniformly therein or concentrated at the surface, center, or at some other portion thereof. In this embodiment the chips perform a dual function, as a bulking agent and as an abrading agent.

The property of the pellet which is taken advantage of according to the present invention is the melting or softening point of the material from which the pellet is produced. In order to utilize this property, the melting point must be lower than that of the material from which the parts are fabricated. When a metal such as steel, zinc, copper, brass, or the like, is used, many materials having a lower melting point are available. Among such materials are Woods metal, various solid thermoplastic resins, waxes, and frozen liquids such as ice. In utilizing these materials, the chips or pellets may be prepared therefrom by any suitable means such as casting, molding, machining, or cutting. The chips may be so utilized in conjunction with a separate abrasive material, generally in finely divided or particulate form. Alternatively, the abrasive material may be dispersed or imbedded in the material or matrix from which the chips are fabricated while the matrix material is maintained in the molten or softened state. The abrasive imbedded material may then be fabricated by any suitable process, for example one of those described above.

In carrying out the finishing process, the finishing material, including chips as prepared iri either form described above, are placed together with the parts to be finished in a suitable finishing machine. The temperature of the finishing mixture should preferably be controlled so that the chips do not reach their melting temperature during the finishing process. This is particularly important in the case where ice is used as bodying agent or as matrix for fabricating the chips, and it is in that case preferred that the finishing process be carried out under cooling conditions. After the finishing process has been carried to the required degree, the parts are transported into a heating chamber, either in the form of a liquid bath as shown in FIG. 1, or an air-heating chamber as shown in FIG. 2. For example, when Woods metal is utilized for the chips, a water bath maintained at a temperature of about 170 F.-200 F. accomplishes fusion of the metal, thereby dislodging the chips. When thermoplastic resins or waxes are utilized, a somewhat higher temperature may be required and the apparatus of FIG. 2 is more desirable. When ice chips are utilized, either as bulking agent or as matrix, it is only necessary to immerse the parts containing entrapped ice chips in a water bath maintained at room temperature or in air at room temperature to accomplish a complete separation. Of course, higher temperature water or steam, preferably in jet form, speed up the process considerably. Because of the excellent results and great convenience experienced by employing ice chips either as a matrix or as bulking agent, its employment constitutes a preferred embodiment of the invention.

When frozen carbon dioxide chips are utilized, the chips may be sublimed to a suificient degree merely by exposing the parts to air maintained at room temperature or alternatively by immersing the parts in a water bath which may also be maintained at room temperature. Since the portions of the chips in actual contact with the parts are warmed first, the chips may be released when only a small portion thereof has sublimed. Other gases in solid phase may also be used with the same effect, for example, solid nitrogen.

Among the various abrasive materials which may be used in particulate form, either as a separate component or imbedded or dispersed in the chips, are emery, carborundum, diamond dust, and many others known in the art.

As to the material which of necessity must undergo a change of state in accord with the invention, it is only necessary that the pellets be composed of such material, i.e., that suflicient of the said material which undergoes the change of state be present in the pellet so that the necessary change in form of the pellet be effected, whether only one or more than one material comprises the pellet.

It is to be understood that the invention is not limited to the exact details of construction, operation, or exact materials or embodiments shown and described, as obvious modifications and equivalents will be apparent to one skilled in the art, and the invention is therefore to be limited only by the scope of the appended claims.

I claim:

1. In a method for finishing parts which comprises subjecting said parts and a finishing composition to movement causing relative motion between said parts and said finishing composition, and subsequently separating said parts from said finishing composition, the improvement wherein said finishing composition comprises a plurality of pellets and an abrasive material, said pellets being comprised of the solid phase of a material which is a gas at room temperature, and wherein said method comprises applying external cooling. to said parts and finishing composition to maintain said pellets in the solid phase during the finshing process and, after finishing, the further step of subjecting said parts to at least the sublimation temperature of said solid gas, whereby pellets which have become entrapped by said parts during the finishing process are disengaged.

2. The method of claim 1 wherein said gas is carbon dioxide.

3. In a method for finishing parts which comprises subjecting said parts and a finishing composition to movement causing relative motion between said parts and said finishing composition, and subsequently separating said parts from said finishing composition, the improvement wherein said finishing composition comprises a plurality of pellets comprising a matrix of the solid phase of a material which is a gas at room temperature and abrasive material dispersed therein, and wherein said method comprises, after finishing, the further step of subjccting said parts to at least the sublimation temperature of said solid gas but lower than the melting point of said parts, whereby pellets which have become entrapped by said parts during the finishing process are disengaged.

4. The method of claim 3 wherein said gas is carbon dioxide.

5. In a method according to claim 3, the improvement wherein external cooling is applied during the finishing process, thereby maintaining said pellets in the solid state.

6. In a method for finishing, arts which comprises subjecting said parts and a finishing composition to move ment causing relative motion between said parts and said finishing composition, and subsequently separating said parts from said finishing composition, the improvement wherein said finishing composition comprises the solid phase of a material which is a gas at room temperature and an abrasive material, and wherein said method comprises applying external cooling to said parts and finishing composition to maintain said material in the solid phase during the finishing process and, after finishing, the further step of subjecting said parts to at least the sublimation temperature of said solid material to accom- 10 plish the removal of said material.

DONALD J. AR NOLD, Primary Examiner.

US. Cl. X.R. 5l-293, 298, 305 

1. IN A METHOD FOR FINISHING PARTS WHICH COMPRISES SUBJECTING SAID PARTS AND A FINISHING COMPOSITION TO MOVEMENT CAUSING RELATIVE MOTION BETWEEN SAID PARTS AND SAID FINISHING COMPOSITION, AND SUBSEQUENTLY SEPARATING SAID PARTS FROM SAID FINISHING COMPOSITION, THE IMPROVEMENT WHEREIN SAID FINISHING COMPOSITION COMPRISES A PLURALITY OF PELLETS AND AN ABRASIVE MATERIAL, SAID PELLETS BEING COMPRISED OF THE SOLID PHASE OF A MATERIAL WHICH IS A GAS AT ROOM TEMPERATURE, AND WHEREIN SAID METHOD COMPRISES APPLYING EXTERNAL COOLING TO SAID PARTS AND FINISHING COMPOSITION TO MAINTAIN SAID PELLETS IN THE SOLID PHASE DURING THE FINISHING PROCESS AND, AFTER FINISHING, THE FURTHER STEP OF SUBJECTING SAID PARTS TO AT LEAST THE SUBLIMATION TEMPERATURE OF SAID SOLID GAS, WHEREBY PELLETS WHICH HAVE BECOME ENTRAPPED BY SAID PARTS DURING THE FINISHING PROCESS ARE DISENGAGED.
 2. THE METHOD OF CLAIM 1 WHEREIN SAID GAS IS CARBON DIOXIDE. 